The search has focused in the past week on hospitals, stores, parks and other public spaces where Tripathi could be, but authorities have found no signs of him.

The search, which has been spearheaded by the Providence Police Department and the Brown University Department of Public Safety, has now expanded to Boston, Connecticut, New York and Philadelphia, according to a statement from the school.

The FBI has joined the search.

"[It's] on the small hope he just decided to go somewhere and is OK. People have been posting fliers and visiting places a young person without an ID or money would go," Tripathi said.

Sunil Tripathi grew up in Radnor, Pa., as the youngest of three siblings, who have all attended Brown University, his sister said.

"He's just a really quiet smart kid. All three of us went to Brown and he outscored us in all of our grades," Sangeeta Tripathi said.

"We're a very, very close family and when we heard [he was missing], we were trying to frantically look for photos. We had trouble finding a photo [where] we all weren't so physically close in the image," she said.

Sunil Tripathi was last seen wearing a pair of blue jeans, a black Eastern Mountain Sports ski jacket, glasses and a Philadelphia Eagles wool hat. He is 6-feet tall and weighs 130 pounds.

Anyone with information is asked to contact the Providence Police Department.